The relationship of interaction forces in the protein adsorption onto polymeric microspheres

The relationship between hydrophobic and electrostatic interactions in protein adsorption was studied with various sulfonated microspheres, and it was compared with carboxylated microspheres. Hydrophobic interaction governed the adsorption in the low sulfonated microspheres and electrostatic interaction did in the high sulfonated ones. The transition point was observed when the two forces were exactly balanced, but it was shifted to the left compared to the case of the carboxylated microspheres. The above adsorption experiments with different kinds of surface functionality revealed the following general mechanism of protein adsorption. The protein adsorption mainly occurs by hydrophobic interaction when the hydrophobic surface is slightly modified with weak or strong acid, while it primarily occurs by hydrogen bonding (or electrostatic) interaction when the surface is mostly modified with weak (or strong) acid. The adsorption by electrostatic interaction is higher than that by any other interactions, but the rate of adsorption is slowest.